Myosin mRNA Research Articles

The Effect of SERCA Activation on Functional Characteristics and Signaling of Rat Soleus Muscle upon 7 Days of Unloading.

Skeletal muscle abnormalities and atrophy during unloading are accompanied by the accumulation of excess calcium in the sarcoplasm. We hypothesized that calcium accumulation may occur, among other mechanisms, due to the inhibition of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) activity. Consequently, the use of the SERCA activator will reduce the level of calcium in the sarcoplasm and prevent the negative consequences of muscle unloading. Wistar rats were randomly assigned into one of three groups (eight rats per group): control rats with placebo (C), 7 days of unloading/hindlimb suspension with placebo (7HS), and 7 days of unloading treated with SERCA activator CDN1163 (7HSC). After seven days of unloading the soleus muscle, the 7HS group displayed increased fatigue in the ex vivo test, a significant increase in the level of calcium-dependent CaMK II phosphorylation and the level of tropomyosin oxidation, as well as a decrease in the content of mitochondrial DNA and protein, slow-type myosin mRNA, and the percentage of slow-type muscle fibers. All of these changes were prevented in the 7HSC group. Moreover, treatment with CDN1163 blocked a decrease in the phosphorylation of p70S6k, an increase in eEF2 phosphorylation, and an increase in MuRF-1 mRNA expression. Nevertheless, there were no differences in the degree of fast and slow muscle fiber atrophy between the 7HS and 7HSC groups. Conclusion: SERCA activation during 7 days of unloading prevented an increase in soleus fatigue, the decrease of slow-type myosin, mitochondrial markers, and markers of calcium homeostasis but had no effect on muscle atrophy.

A Prochlorperazine-Induced Decrease in Autonomous Muscle Activity during Hindlimb Unloading Is Accompanied by Preserved Slow Myosin mRNA Expression.

Skeletal muscle disuse leads to pathological muscle activity as well as to slow-to-fast fiber-type transformation. Fast-type fibers are more fatigable than slow-type, so this transformation leads to a decline in muscle function. Prochlorperazine injections previously were shown to attenuate autonomous rat soleus muscle electrical activity under unloading conditions. In this study, we found that prochlorperazine blocks slow-to-fast fiber-type transformation in disused skeletal muscles of rats, possibly through affecting calcium and ROS-related signaling.

Knocking down the expression of the molecular motors, myosin A, C and F genes in Toxoplasma gondii to decrease the parasite virulence

Toxoplasmosis is a serious parasitic infection and novel therapeutic options are highly demanded to effectively eliminate it. In current study, Toxoplasma gondii myosin A, C and F genes were knocked down using small interference RNA (siRNA) method and the parasite survival and virulence was evaluated in vitro and in vivo. The parasites were transfected with specific siRNA, virtually designed for myosin mRNAs, and co-cultured with human foreskin fibroblasts. The transfection rate and the viability of the transfected parasites were measured using flow cytometry and methyl thiazole tetrazolium (MTT) assays, respectively. Finally, the survival of BALB/c mice infected with siRNAs-transfected T. gondii was assessed. It was demonstrated that a transfection rate of 75.4% existed for siRNAs, resulting in 70% (P = 0.032), 80.6% (P = 0.017) and 85.5% (P = 0.013) gene suppression for myosin A, C and F in affected parasites, respectively, which was subsequently confirmed by Western blot analysis. Moreover, lower parasite viability was observed in those with knocked down myosin C with 80% (P = 0.0001), followed by 86.15% (P = 0.004) for myosin F and 92.3% (P = 0.083) for myosin A. Considerably higher mouse survival (about 40 h) was, also, demonstrated in mice challenged with myosin siRNA-transfected T. gondii, in comparison with control group challenged with wild-type parasites. In conclusion, myosin proteins knock down proposes a promising therapeutic strategy to combat toxoplasmosis.

The role of MAP-kinase p38 in the m. soleus slow myosin mRNA transcription regulation during short-term functional unloading

The unloading of postural muscles leads to the changes in myosins heavy chains isoforms (MyHCs) mRNAs transcription pattern, that cause severe alterations of muscle functioning. Several transcription factors such as NFATc1 and TEAD1 upregulate slow MyHC mRNA transcription, and p38 MAP kinase can phosphorylate NFAT and TEAD1, causing their inactivation. However, the role p38 MAP kinase plays in MyHCs mRNAs transcription regulation in postural soleus muscle during unloading remains unclear. We aimed to investigate whether pharmacological inhibition of p38 MAPK during rat soleus unloading would prevent the unloading-induced slow-type MyHC mRNA transcription decrease by affecting calcineurin/NFATc1 or TEAD1 signaling. Male Wistar rats were randomly assigned to three groups: cage control (C), 3-day hindlimb suspended group (3HS) and 3-day hindlimb suspended group with the daily oral supplementation of 10 mg/kg p38 MAPK inhibitor VX-745 (3HS + VX-745). 3 days of hindlimb suspension caused the significant decreases of slow MyHC and slow-tonic myh7b mRNAs transcription as well as the decrease of NFATc1-dependent MCIP1.4 mRNA transcription in rat soleus muscles compared to the cage control. P38 MAP-kinase inhibition during hindlimb suspension completely prevented slow MyHC mRNA content decrease and partially prevented slow-tonic myh7b and MCIP1.4 mRNAs transcription decreases compared to the 3HS group. We also observed NFATc1 and TEAD1 myonuclear contents increases in the 3HS + VX-745 group compared to both 3HS and C groups (p < 0.05). Therefore, we found that p38 inhibition counteracts the unloading-induced slow MyHC mRNA transcription downregulation and leads to the activation of calcineurin/NFAT signaling cascade in unloaded rat soleus muscles.

The Molecular Basis of Drug Discovery Targeting the Regulatory Mechanism of MAPK Signaling via the Spatial Regulation of RNA-binding Proteins

Mitogen-activated protein kinase (MAPK) is a highly conserved serine/threonine kinase that regulates multiple cellular processes such as cell proliferation, differentiation, apoptosis, and inflammation. Rnc1 has been identified as a regulator of Pmk1 MAPK signaling, a homologue of extracellular signal-regulated kinase (ERK)-1 MAPK in mammals. Rnc1 encodes a K-homology (KH)-type RNA-binding protein (RBP). Previously, it was reported that Rnc1 acts as a negative regulator of Pmk1 MAPK signaling through the mRNA stabilization of Pmp1, the MAPK phosphatase for Pmk1 in our laboratory. We analyzed the spatial regulation of Rnc1 and discovered that Rnc1 is exported from the nucleus by the mRNA-export system. The nuclear export of Rnc1 is important for exerting its function to stabilize Pmp1 mRNA. Therefore, the spatial regulation of Rnc1 affects MAPK signaling activity. We also reported that Nrd1, an RRM-type RBP, plays a critical role in cytokinesis by binding to and stabilizing myosin mRNA. Notably, Rnc1 and Nrd1 localize to stress granules (SGs) in response to various environmental stresses. Moreover, SG formation is inhibited in the Nrd1 or Rnc1 deletion cells, whereas the overproduction of Nrd1 or Rnc1, as well as that of mammalian RBP TIA-1, induces granule formation. These data show that Nrd1 and Rnc1 regulate SG formation as a novel SG component. Alterations of SG formation are linked to neurodegenerative diseases and resistance to anti-cancer drugs, thus conferring remarkable clinical importance to SGs. This review discusses the spatial regulation of RBPs or SG formation as novel targets for drug discovery.

PO-095 Effects of dynamic foot stimulation on GSK-3 beta signaling pathway in rat soleus muscle under hindlimb unloading

Objective It is known that under simulated microgravity GSK-3 beta phosphorylation (Ser 9) is decreased [Mirzoev et al., 2016] which is associated with the activation of its kinase activity. GSK-3 beta activation may lead to NFATc1 export from myonuclei resulting in a slow-to-fast myosin shift in soleus muscle and may cause a decrease in muscle oxidative capacity and protein synthesis [Glass, 2003, Theeuwes et al, 2017].&#x0D; It was demonstrated that GSK-3 beta Ser 9 phosphorylation is decreased in response to nitric oxide synthase inhibition [Martins et al., 2011]. Under unloading conditions, the content of NO as well as nitric oxide synthase is attenuated in rat soleus muscle [Tidball et al., 1998; Lomonosova et al, 2011]. Dynamic foot stimulation (DFS) of the soles of the feet results in an increase of neuromuscular activation [Muller et al., 2005] of the lower limb muscles and prevents nitric synthase content decrease during 7-day exposure to dry immersion [Moukhina et al, 2004; Shenkman et al., 2004]. The aim of our study was to analyze the effect of rat dynamic foot stimulation during early unloading on GSK-3 beta phosphorylation and some of its downstream targets.&#x0D; Methods Male Wistar rats were randomly assigned to vivarium control, 1-day unloading and 1-day&#x0D; unloading with DFS. The pressure stimulation protocol mimicked the normal animal walking (104 mm Hg pressure, 4 Hz frequency and 250 ms signal duration) for a total of 20 min followed by a 10-min rest interval for 4 hours.&#x0D; Results We found that 1-day unloading caused a significant decrease (p˂ 0.025) in NFATc1 nuclear content as well as slow myosin (MHC I (beta) isoform) mRNA expression. In the 1-day unloading group, the level of glycogen synthase 1 phosphorylation (Ser 641), which is a direct GSK-3 beta target, was significantly higher than that in the control group, although a decrease in GSK-3 beta Ser 9 phosphorylation in the 1-day unloaded group was not statistically significant compared to the control group. However, in the DFS-treated unloaded rats the level of GSK-3 beta phosphorylation was significantly higher than in the untreated unloaded rats. NFATc1 nuclear content, slow myosin mRNA expression and glycogen synthase 1 phosphorylation (Ser 641) did not differ from the control group. The glycogen content in soleus muscles of both unloaded groups was higher than in the control group, which is in accordance with previous studies [Henriksen and Tischler, 1988], but in DFS subjected unloaded group the glycogen content was higher compared to the untreated unloaded group.&#x0D; Conclusions Thus, we found that dynamic foot stimulation during 1-day hindlimb unloading leads to GSK-3 beta inactivation and prevention of both NFATc1 myonuclei export and the decrease in MyHC I beta expression.&#x0D; The study was supported by the Russian Foundation for Basic Research grant #17-29-1029 and Basic Research Program of the IBMP, RAS. The authors express their deep gratitude to Prof. Inessa B. Kozlovskaya for useful recommendations concerning the design of the study.

PL - 032 Physiological triggers involved in reduced slow myosin expression in disused postural muscle

PL - 032 Physiological triggers involved in reduced slow myosin expression in disused postural muscle

Construction of engineered corpus cavernosum with primary mesenchymal stem cells in vitro

Various methods have been used to reconstruct the penis. The objective of this study was to investigate the feasibility of constructing engineered corpus cavernosum with primary mesenchymal stem cells (MSCs) in a rabbit model in vitro. Acellular corporal matrices (ACMs) were obtained from adult rabbit penile tissues through an established decellularization procedure. MSCs were separated, purified, and then seeded on ACMs to construct engineered corpus cavernosum. The seeded ACMs were subsequently cultured in an incubator for 14 days. Histological analyses showed that MSCs seeded on the ACMs had proliferated and were well distributed. Detection of CD31, vWF, smooth muscle actin (SMA), and myosin protein as well as vWF and myosin mRNA revealed that the MSCs had differentiated into endothelial cells and smooth muscle cells. In addition, cell morphology of the engineered corpus cavernosum was directly observed by transmission electron microscopy. This study demonstrated that engineered corpus cavernosum could be successfully constructed using primary MSCs in vitro. This technology represents another step towards developing engineered corpus cavernosum in vitro.

Reminiscences on my life with RNA: a self-indulgent perspective.

Reminiscences on my life with RNA: a self-indulgent perspective.

Histological changes and changes in the myosin mRNA content of the porcine masticatory muscles after masseter treatment with botulinum toxin A

Botulinum toxin A (Botox) is increasingly used for treatment of muscle hyperfunction. For a better understanding of the possible morphologic and chewing changes in patients induced by a therapy with Botox, muscle fiber and myosin heavy chain (MyHC) mRNA alterations were examined in this animal study. The investigation was carried out on 14-week-old pigs (seven treated animals, eight controls; calculated animal size with a power of 0.5). To initialise the total immobilisation of the right masseter, the Botox injection was distributed into ten areas. After a 56-day period, muscle tissue was taken from the left and right side of the masseter (three regions), temporal (two regions), medial pterygoid and geniohyoid muscles using a standardized method. The muscle fiber cross sections were examined immunohistochemically. Fiber staining was accomplished with antibodies to specific MyHC isoforms. The MyHC mRNA changes were analysed using real-time RT-PCR. Muscles adapt to such stress by changing fiber types and MyHC mRNA content. Paralysed masseters display atrophic changes while other masticatory muscles show hypertrophic changes. The results indicated that the typical distributions of type IIa und IIb fiber types in masticatory muscles were increased in the masseter muscles due to Botox application. On the other hand, the masseters without Botox in the treated group showed a significant increase of type I MyHC. Application of Botox may lead to uncontrolled structural changes in affected and unaffected muscles. Treatment of muscle hypertrophy with Botox may cause muscle imbalance.

Ontogenetic effects of diet during early development on growth performance, myosin mRNA expression and metabolic enzyme activity in Atlantic cod juveniles reared at different salinities

This study investigates the effect of diet during early development on growth and metabolic capacity in the juvenile stage of Atlantic cod. Growth in three groups of Atlantic cod juveniles (10–70 g) was measured at two salinities (15‰ or 32‰) in combination with two temperatures (10 °C or 14 °C). Groups of cod from a single egg batch differed by having been fed with rotifers (R) or natural zooplankton (Z) during the first 36 days post hatch. A third group was fed zooplankton from 1 to 22 dph, after which diet changed to rotifers from 22 to 36 dph (ZRZ). All fish were weaned at 36 dph. Juveniles from the Z and ZRZ groups performed equally well under all experimental conditions, but fish that had received rotifers as a larval diet showed overall significantly lower growth rates. Growth was significantly enhanced by reduced salinity. Metabolic enzyme activity and relative myosin mRNA expression levels were not affected by larval diet. Muscle AAT and MDH were affected by salinity while these enzymes in liver tissue were affected by the interaction between salinity and temperature. Metabolic enzymes were stronger correlated with fish size than growth rates. Our results indicate that larval diet has a pronounced effect on juvenile growth rates under varying environmental conditions as optimal larval diet (zooplankton) increased juvenile growth rates significantly. Metabolic enzyme activity and relative myosin mRNA expression were not affected by larval history, which suggests that the persisting juvenile growth difference is not a result of differing metabolic capacity.

A Family of microRNAs Encoded by Myosin Genes Governs Myosin Expression and Muscle Performance

Myosin is the primary regulator of muscle strength and contractility. Here we show that three myosin genes, Myh6, Myh7, and Myh7b, encode related intronic microRNAs (miRNAs), which, in turn, control muscle myosin content, myofiber identity, and muscle performance. Within the adult heart, the Myh6 gene, encoding a fast myosin, coexpresses miR-208a, which regulates the expression of two slow myosins and their intronic miRNAs, Myh7/miR-208b and Myh7b/miR-499, respectively. miR-208b and miR-499 play redundant roles in the specification of muscle fiber identity by activating slow and repressing fast myofiber gene programs. The actions of these miRNAs are mediated in part by a collection of transcriptional repressors of slow myofiber genes. These findings reveal that myosin genes not only encode the major contractile proteins of muscle, but act more broadly to influence muscle function by encoding a network of intronic miRNAs that control muscle gene expression and performance.

Genome‐wide mapping of myosin protein‐RNA networks suggests the existence of specialized protein production sites

Motor proteins can organize posttranscriptional processes by transporting ribonucleoprotein complexes to specific locations. To investigate a possible role of myosin proteins in gene expression control, I have identified mRNAs associated with five myosin heavy chains in the fission yeast Schizosaccharomyces pombe, by purifying the proteins and identifying bound transcripts using DNA microarrays. Each myosin coimmunoprecipitated with 5-13 different mRNAs (approximately 0.1-0.2% of all genes), including those encoding four different myosin heavy chains. Moreover, one of the myosins (Myo1) interacted with mRNAs encoding components of the cortical actin cytoskeleton. These interactions were not observed in control immunoprecipitates. A myosin-specific chaperone (Rng3) that interacts cotranslationally with myosin mRNAs was essential for the association between myosin proteins and transcripts but not between Myo1 and other mRNAs. Finally, proteins encoded by the Myo1-associated mRNAs immunoprecipitated each other's transcripts, but not myosin mRNAs. These interactions suggest the existence of two distinct myosin-containing ribonucleoprotein complexes: those containing myosin mRNAs and those associated with Myo1. They are distinguished by their mRNA composition, requirement for the Rng3 chaperone and the presence of nonmyosin cytoskeletal proteins. I propose that these complexes represent specialized sites for the production of myosin proteins and the assembly of cytoskeletal components, respectively.

Role of the RNA-binding Protein Nrd1 and Pmk1 Mitogen-activated Protein Kinase in the Regulation of Myosin mRNA Stability in Fission Yeast

Myosin II is an essential component of the actomyosin contractile ring and plays a crucial role in cytokinesis by generating the forces necessary for contraction of the actomyosin ring. Cdc4 is an essential myosin II light chain in fission yeast and is required for cytokinesis. In various eukaryotes, the phosphorylation of myosin is well documented as a primary means of activating myosin II, but little is known about the regulatory mechanisms of Cdc4. Here, we isolated Nrd1, an RNA-binding protein with RNA-recognition motifs, as a multicopy suppressor of cdc4 mutants. Notably, we demonstrated that Nrd1 binds and stabilizes Cdc4 mRNA, thereby suppressing the cytokinesis defects of the cdc4 mutants. Importantly, Pmk1 mitogen-activated protein kinase (MAPK) directly phosphorylates Nrd1, thereby negatively regulating the binding activity of Nrd1 to Cdc4 mRNA. Consistently, the inactivation of Pmk1 MAPK signaling, as well as Nrd1 overexpression, stabilized the Cdc4 mRNA level, thereby suppressing the cytokinesis defects associated with the cdc4 mutants. In addition, we demonstrated the cell cycle-dependent regulation of Pmk1/Nrd1 signaling. Together, our results indicate that Nrd1 plays a role in the regulation of Cdc4 mRNA stability; moreover, our study is the first to demonstrate the posttranscriptional regulation of myosin expression by MAPK signaling.

Physiological factors influencing the growth of skeletal muscle.

The growth of muscle can be regulated by developmental changes or by alterations in hormone levels or in the rate or amount of work demanded. The mechanisms and structures involved in growth processes can be studied by controlling these factors. The models used are chicken anterior latissimus dorsi (ALD) muscle under the influence of overloading and rabbit tibialis anterior (TA) muscle under the influence of chronic nerve stimulation. Both models involve changes in the isoform of myosin that is expressed. Methods of study include quantitative ultrastructural analysis, immunofluorescence and in situ mRNA hybridization. In overloaded chick ALD fibres polysomes are nonuniformly distributed between the myofibrils and in a peripheral annulus even though subcellular concentrations of the new isoform are not found. In normal rabbit muscle the highest concentration of myosin mRNA detected by in situ hybridization is found in the subsarcolemmal zone. In stimulated TA polysomes are found between myofibrils. It appears that the myosin mRNA accumulates at specific cell locations before translation; then diffusion of isomyosin and rapid exchange into myofibrils follows. Therefore, regulation of growth may be possible at the transcriptional, translational and assembly stages.

Myosin expression levels and enzyme activity in juvenile spotted wolffish (Anarhichas minor) muscle: a method for monitoring growth rates

The activity of glycolytic enzymes and the expression levels of myosin RNA was monitored in the white muscle of juvenile spotted wolffish (Anarhichas minor) reared under different temperature regimes. A group of individually tagged juvenile spotted wolffish was reared for 6 months at 4, 6, 8, and 12 °C. After the rearing trial, biopsy samples were taken from white muscle of each individual and the relationship between individual growth, enzyme activity, and myosin expression was investigated. A positive relationship between the activities of two glycolytic enzymes (pyruvate kinase and lactate dehydrogenase) and individual growth rate was observed. Using real-time polymerase chain reaction (PCR) and specially developed primers for myosin mRNA and 18S rRNA for spotted wolffish, we were able to detect differences in the relative myosin expression between experimental groups, and a positive relationship between myosin expression and specific growth rates was observed. These methods may be useful as an indicator of growth rate in wild fish and a fast and reliable indicator of growth potential under culture conditions. The method also has the potential to measure differences in white muscle synthesis in fish reared under variable environmental parameters and during different life history stages.

Quantification by real-time PCR of developmental and adult myosin mRNA in rat muscles

A real-time RT-PCR assay using newly designed primers was developed to analyze developmental and adult MHC mRNA expression both in skeletal muscles and single fibers. Only 4 ng of total RNA was necessary for the analysis of the relative mRNA expression of MHC genes. Different validation steps were realized concerning both specificity and sensitivity of each primer set, and linearity and efficiency of each real-time PCR amplification. Then, quantification of MHC mRNA in neonatal and adult muscles as well as in single fibers was done by the Δ C T method, with CycA gene as the reference gene. Due to a higher sensitivity than that of a competitive PCR method, we demonstrated that this assay is suitable to study very low level of MHC mRNA expression as developmental MHC in adult muscle and to quantify mRNA from very small samples.

Highlights from the Literature

Highlights from the Literature

The Effects Of Loading And Stretch On Transcriptional And Translational Markers

INTRODUCTION To date, literally thousands of studies have examined issues related to muscle atrophy and hypertrophy as reflected by changes in radial size. In contrast, less than 100 studies have examined issues related to the underlying biology of longitudinal growth. Given this consideration, the objective of this study was to contrast changes in transcriptional and translational capacity following: 1) recovery of cross-sectional area via reloading of atrophied muscles; and 2) longitudinal growth as induced by chronic stretch via distraction. METHODS Female Sprague-Dawley rats were randomly assigned to the following groups: 1) control (CON); 2) reloading (RELOAD); and 3) distracted (DIS). Animals assigned to the RELOAD group underwent 4 wks of hindlimb suspension prior to the reloading phase. They were then allowed to undergo normal cage activity for either 4 or 8 days, at which time they were sacrificed. Animals in the DIS group were sacrificed 4 and 8 days following the onset of stretch. The soleus muscle was stretched at a rate of 0.5 mm/day. RESULTS As compared to the CON group, there was a large increase in the concentration of total RNA of the soleus muscle at both the 4 and 8-day time-points for the RELOAD group. Similarly, there was a large increase in the concentration of oligo dT. In contrast, stretch actually produced a small but significant reduction in total RNA, whereas the concentration of oligo dT was unaffected. Reloading also produced large increases in the concentrations of both actin and MHC mRNA levels, whereas just the opposite was observed in the stretched muscles. DISCUSSION Reloading of skeletal muscle produced significant increases in four key markers of growth: i) muscle weight; ii) total RNA pool; iii) the total amount and concentration of mRNA as reflected by oligo dT; and iv) a large increase in the amounts and concentrations of actin and myosin mRNA. Stretch, in contrast, failed to elicit an anabolic profile as defined by our markers. This may be due, in large part, to the joint immobilization that accompanies the stretch model used in this study.

The Effects Of Loading And Stretch On Transcriptional And Translational Markers

INTRODUCTION To date, literally thousands of studies have examined issues related to muscle atrophy and hypertrophy as reflected by changes in radial size. In contrast, less than 100 studies have examined issues related to the underlying biology of longitudinal growth. Given this consideration, the objective of this study was to contrast changes in transcriptional and translational capacity following: 1) recovery of cross-sectional area via reloading of atrophied muscles; and 2) longitudinal growth as induced by chronic stretch via distraction. METHODS Female Sprague-Dawley rats were randomly assigned to the following groups: 1) control (CON); 2) reloading (RELOAD); and 3) distracted (DIS). Animals assigned to the RELOAD group underwent 4 wks of hindlimb suspension prior to the reloading phase. They were then allowed to undergo normal cage activity for either 4 or 8 days, at which time they were sacrificed. Animals in the DIS group were sacrificed 4 and 8 days following the onset of stretch. The soleus muscle was stretched at a rate of 0.5 mm/day. RESULTS As compared to the CON group, there was a large increase in the concentration of total RNA of the soleus muscle at both the 4 and 8-day time-points for the RELOAD group. Similarly, there was a large increase in the concentration of oligo dT. In contrast, stretch actually produced a small but significant reduction in total RNA, whereas the concentration of oligo dT was unaffected. Reloading also produced large increases in the concentrations of both actin and MHC mRNA levels, whereas just the opposite was observed in the stretched muscles. DISCUSSION Reloading of skeletal muscle produced significant increases in four key markers of growth: i) muscle weight; ii) total RNA pool; iii) the total amount and concentration of mRNA as reflected by oligo dT; and iv) a large increase in the amounts and concentrations of actin and myosin mRNA. Stretch, in contrast, failed to elicit an anabolic profile as defined by our markers. This may be due, in large part, to the joint immobilization that accompanies the stretch model used in this study.